Project abstract The benefit some hearing of of processing and most advanced signal-processing algorithms used in digital hearing aids have improved average hearing aid and satisfaction. However, the benefit received from digital hearing aids is still highly variable, with individuals reporting much more benefit than others. An important issue is what levels of advanced aid processing are necessary to achieve success with hearing aids in individual listeners. Every form nonlinear signal processing has its own set of trade-offs of improved audibility versus increased modification the signal caused by the signal processing. There are no effective procedures for determining how the should be adjusted for the individual listener so that it is optimally suited to the listener's auditory cognitive abilities. The long term goal of this research i s to uide the selection of signal processing that is appropriate for individual older adults wearing hearing aids in their own listening environments. g In the proposed supplement, we will expand the first specific aim--to characterize variability in response to signal manipulation among older adults--by including adults with Alzheimer's dementia and a precursor, amnestic mild cognitive impairment. As in the parent grant, the supplement work will measure patient outcomes for a comparison of hearing aid signal processing that represent different levels of signal modification. We hypothesize that adults with Alzheimer's dementia represent an extreme case of restricted cognitive ability, such that very low working memory capacity and overall reduced cognitive capacity will limit benefit from advanced signal processing. Thus, we hypothesize that adults with Alzheimer's dementia (or amnestic mild cognitive impairment) will receive greatest benefit from acoustically simple, high-fidelity hearing aid processing that minimally alters the acoustic signal. The primary outcome of speech intelligibility will be supplemented by additional outcomes designed for adults with dementia: conversation analysis to quantify conversation breakdowns and repair behaviors as a function of hearing aid signal manipulations; and communication partner perceptions of conversation difficulty. This dataset will allow us to extend our model-based approach to examine effects of signal processing for patients with a wide range of cognitive abilities. The data collected during the supplement will also inform the second specific aim of the parent grant, in which the clinical toolset will be implemented in a computer-based application that can guide audiologists in the fitting and adjustment of signal processing based on individual listener characteristics. If feasible, we may also include adults with Alzheimer's dementia in the third specific aim of the parent grant, clinical validation of the toolset. In conjunction with the parent dataset, the questions addressed in this supplement will increase our understanding and application of the effects of hearing aid processing in realistic conversational situations, while considering specific abilities that affect response to signal processing in older adults with a wide range of normal and abnormal cognitive abilities.